There is already available HTTP (Hyper Text Transfer Protocol) used to transfer documents in HTML (Hyper Text Markup Language) between the WWW (World Wide Web) and a Web browser.
There is disclosed in the Japanese Patent Application Laid Open No. 2003-150096, for example, an information providing system that generates ad information in HTML format as to merchandises (articles) set out in a predetermined space, such as display shelves in a store, by acquiring and consolidating information on the merchandise acquired from a radio tag preattached on each piece of the merchandise. Thus, the user of the information providing system, such as a merchandise purchaser, can observe the ad information without visiting the store.
In addition to the above-mentioned HTTP, the SIP (Session Initiation Protocol; an IETF Standard RFC2543) is also known. For communication by the VoIP (Voice over Internet Protocol) that encapsulates voice into an IP packet to enable voice communication over an IP network, for example, it is necessary to make, by a party at one end of the IP network, a sequence of information exchange operations including the acquisition of information on a party at the other end with which the one-end party is going to communicate, making of a call to the latter, reception of a response from the other-end party, etc. For this purpose, a call control protocol, such as SIP, is used. In a communication system using the IP telephone network, the SIP enables transfer of a picture, text data, a data file and streaming data in addition to a high-quality voice communication.
The general procedure of the communication using the SIP will be explained below. For real-time data transfer between communication devices, SIP-based call control is made in addition to the real-time data transfer. FIG. 1 shows a communication procedure in which a client CA (Bob) calls a client CB (Alice). Message data is transferred between the clients CA and CB under the call control of the SIP-based VoIP. In FIG. 1, it is assumed that a communication device P of Bob (bob@bbb.com) is a calling end while and a communication device Q of Alice (alice@aaa.com) is a called end and data (a message) is transferred between the communication devices P and Q of both the VoIP clients.
The SIP messages include a request message to be sent from UAC (UA Client) as a calling end to UAS (UA Server) as a called end and a response message to be returned from the UAS to UAC. The body of a request message includes session information based on the SDP (Session Description Protocol). Also, a predetermined response, such as an OK response, includes a SDP message to select a codec that is to be used for the communication.
A communication over the telephone between these clients CA (Bob) and CB (Alice) will be described by way of an example. First, Bob at the calling end picks up the handset from his communication device P and dials Alice's phone number. Thus, an INVITE for requesting joining the session is sent to the IP communication device Q of Alice at the called end (in step D11). The INVITE includes a SDP message that stated therein media information on a device that Bob's communication device P will use or the like. It should be noted that each of the messages which will be transferred thereafter includes some destination information. Referring to such destination information, etc., an IP telephone server or call controlling means at each end can send a message to a predetermined communication device. When the INVITE from Bob's IP communication device P arrives at Alice's communication device Q, the latter will send a response “100 Trying” to Bob's communication device P (in step D12). It should be noted that the above step corresponds to the process in the common telephone system from the silent-state up to the connection with the called end until the moment the calling end is connected to the called end.
Then, a response “180 Ringing” is sent from Alice's communication device Q to Bob's communication device P (in step D13). This step corresponds to the ringing of Alice's communication device Q. The responses “100 Trying” and “180 Ringing” indicate that the request has been received and is being processed at the other end. When Alice picks up the handset from her communication device Q, a response “200 OK” indicating that the request has been accepted is sent to Bob's communication device P (in step D14).
Then, Bob's communication device P at the calling end sends an ACK (acknowledgement) to Alice's communication device Q (in step D15). Thus, a communication port is opened to enable the communication between Bob and Alice. As above, the call control is followed by set-up of RTP/RTCP session and then by transfer of voice or data, such as voice, or voice and picture.
To terminate the communication, a message “BYE” is sent from the communication end at which the handset is first put back on the communication device to the other communication end (in step D16). Namely, the message “BYE” can be issued from either Bob's IP communication device P at the calling end or Alice's IP communication device Q at the called end, at whichever handset has been hung up, and the party having received the message “BYE” sends a response “200 OK” to the sender of the message “BYE” (in step D17).
Note here that while the IP telephone as a telephone over the Internet is rapidly prevailing, a fusion between a real-time communication (mainly over the IP telephone system), such as the IP telephone, and the aforementioned HTTP used mainly in the current Internet network has recently attracted attention in the industry.
However, the HTTP is a protocol for use in transferring text in HTML (Hyper Text Markup Language) between the WWW (World Wide Web) and a Web browser. Namely, it is most effective for communications effected in non-real time. Therefore, in a case where it is tried to use HTTP in fusion with the IP telephone system that is rather strictly required to show a highly real-time performance, it is difficult to provide any means for determining when information about a real-time situation should be coded with HTML, a means for confirming the reliability on information, etc. In actuality, it is difficult to attain a fusion between the IP telephone system and HTTP.